Solid-state image pickup element, method of manufacturing solid-state image pickup element, and electronic apparatus

ABSTRACT

To solve at least one of various problems in an image sensor in a 2PD scheme. A solid-state image pickup element includes a plurality of pixels each including a photoelectric conversion element formed on a silicon substrate, in which some pixels in the plurality of pixels each have the photoelectric conversion element partitioned by a first-type separating region extending in a plate shape in a direction along a thickness direction of the silicon substrate, and other pixels in the plurality of pixels each have the photoelectric conversion element partitioned by a second-type separating region formed with a material different from a material of the first-type separating region, the second-type separating region extending in a plate shape in the direction along the thickness direction of the silicon substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 16/342,314 filed Apr. 16, 2019, which is a national stageapplication under 35 U.S.C. 371 and claims the benefit of PCTApplication No. PCT/JP2017/026643 having an international filing date ofJul. 24, 2017, which designated the United States, which PCT applicationclaimed the benefit of Japanese Patent Application No. 2016-211195 filedOct. 28, 2016, the entire disclosures of each of which are incorporatedherein by reference.

TECHNICAL FIELD

The present technology relates to a solid-state image pickup element, amethod of manufacturing the solid-state image pickup element, and anelectronic apparatus.

BACKGROUND ART

There are roughly three types of auto focus (AF) scheme of a camera:phase-difference AF; contrast AF; and on-sensor phase-difference AF. Theon-sensor phase-difference AF is the latest scheme and has beendeveloped progressively in recent years. Because the on-sensorphase-difference AF has the function of a phase-difference AF sensorincorporated in pixels themselves of an image sensor, the on-sensorphase-difference AF can achieve the phase-difference AF without beingseparately equipped with separator lenses and a phase-difference AFsensor required in the phase-difference AF. In other words, similarly tothe phase-difference AF, the on-sensor phase-difference AFinstantaneously measures the amount of AF deviation, making it possiblefor a set lens to come into focus very quickly.

Patent Document 1 discloses a light-shielding metal scheme that is themainstream of the pixel structure of the on-sensor phase-difference AF.In the light-shielding metal scheme, there are provided a plurality ofpairs of pixels (pupil pixel), in which each pixel is substantially halfcovered with light-shielding metal so as to detect only light thatpasses through one side of the exit pupil of a set lens. The pupil pixelincludes: a first pixel including a first side of a pixel substantiallyhalf covered with the light-shielding metal; and a second pixelincluding a second side of a pixel substantially half covered with thelight-shielding metal.

The first pixel and the second pixel are provided at mutually closepositions in an image sensor. Thus, when the set lens is in focus, afirst received image acquired from the first pixel and a second receivedimage acquired from the second pixel are identical. Meanwhile, when theset lens is out of focus, a shift occurs between the first receivedimage and the second received image, and the images switch betweenfocusing on the near side and focusing on the far side. In such a case,the deviation in focusing of the set lens together with a deviationdirection can be measured instantaneously.

Because the on-sensor phase-difference pixels in the light-shieldingmetal scheme are defective pixels from which an output signal cannot beused for image forming, there is a disadvantage that image quality ofthe image sensor is lower than that of an image sensor having the samenumber of pixels with no on-sensor phase-difference AF.

As a solution for the disadvantage, for example, Patent Document 2 hasproposed a scheme in which, with two divided pixels formed by dividing aphotodiode corresponding to an on-chip lens (hereinafter, referred to asan OCL), ranging is performed using a first received image acquired fromone divided pixel (first divided pixel) and a second received imageacquired from the other divided pixel (second divided pixel), andcumulation of the outputs of the two divided pixels generates an outputfor one pixel that can be used for image forming (hereinafter, referredto as a 2PD scheme). Needless to say, for example, Patent Document 3 hasproposed a concept in which pixels specializing in phase difference asthe 2PD scheme and ordinary pixels used for image generation as a 1PDscheme are mounted mixedly.

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open No.    2012-182332-   Patent Document 2: Japanese Patent Application Laid-Open No.    2001-250931-   Patent Document 3: Japanese Patent Application Laid-Open No.    2015-65269

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

As described above, because the 2PD scheme allows a dense layout of theon-sensor phase-difference pixels in addition to no defective pixel,there is an advantage that accurate acquisition of positional deviationsin the center of gravity of the output of the first divided pixel andthe output of the second divided pixel, allows improvement in AFprecision.

Meanwhile, because a photodiode is divided into two, the volume of thephotodiode as a whole is reduced by a separating portion for pixeldivision, resulting in occurrence of a disadvantage that the relativesensitivity is lower than that of a non-divided pixel (hereinafter,referred to as a 1PD scheme) equivalent in OCL size. Note that, as amethod of separating a phase-difference pixel, metal embedding,oxide-film embedding, and implantation have been known.

However, according to a prototype of an image sensor in the 2PD schemeactually produced by the present inventors, besides a reduction in thevolume of a photodiode, various problems has been found, such as colormixture between divided pixels and occurrence of loss in sensitivity ina separating portion.

The present technology has been made in consideration of the problems,and an object of the present technology is to solve at least one ofvarious problems in an image sensor in the 2PD scheme.

Solutions to Problems

According to one aspect of the present technology, there is provided asolid-state image pickup element that includes a plurality of pixelseach including a photoelectric conversion element formed on a siliconsubstrate, in which some pixels in the plurality of pixels each have thephotoelectric conversion element partitioned by a first-type separatingregion extending in a plate shape in a direction along a thicknessdirection of the silicon substrate, and other pixels in the plurality ofpixels each have the photoelectric conversion element partitioned by asecond-type separating region formed with a material different from amaterial of the first-type separating region, the second-type separatingregion extending in a plate shape in the direction along the thicknessdirection of the silicon substrate.

According to another aspect of the present technology, there is provideda method of manufacturing a solid-state image pickup element thatincludes a plurality of pixels each including a photoelectric conversionelement formed on a silicon substrate, the method including: a step offorming a first-type separating region extending in a plate shape in adirection along a thickness direction of the silicon substrate, thefirst-type separating region partitioning the photoelectric conversionelement of each of some pixels in the plurality of pixels; and a step offorming a second-type separating region with a material different from amaterial of the first-type separating region, the second-type separatingregion extending in a plate shape in the direction along the thicknessdirection of the silicon substrate, the second-type separating regionpartitioning the photoelectric conversion element of each of otherpixels in the plurality of pixels.

According to another aspect of the present technology, there is providedan electronic apparatus that includes a solid-state image pickup elementincluding a plurality of pixels each including a photoelectricconversion element formed on a silicon substrate, in which some pixelsin the plurality of pixels each have the photoelectric conversionelement partitioned by a first-type separating region extending in aplate shape in a direction along a thickness direction of the siliconsubstrate, and other pixels in the plurality of pixels each have thephotoelectric conversion element partitioned by a second-type separatingregion formed with a material different from a material of thefirst-type separating region, the second-type separating regionextending in a plate shape in the direction along the thicknessdirection of the silicon substrate.

Note that the present technology further includes various aspects, suchas an aspect in which the solid-state image pickup element describedabove is performed being incorporated in a different apparatus and anaspect in which the solid-state image pickup element described above isperformed with a different method. The present technology furtherincludes various aspects, such as an aspect in which the method ofmanufacturing a solid-state image pickup element described above isperformed as part of a different method.

Effects of the Invention

According to the present technology, at least one of various problems inan image sensor in a 2PD scheme can be solved. Note that, because theeffects described in the present specification are just exemplary, thepresent technology is not limited to these, and thus additional effectsmay be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of the pixel arrangement of a solid-state imagepickup element according to a first embodiment.

FIG. 2 is a schematic view of the sectional configuration of thesolid-state image pickup element according to the first embodiment.

FIG. 3 illustrates results of an optical-path simulation of incidentlight for photoelectric conversion elements separated with differentseparating films.

FIG. 4 is a graph illustrating the wavelength dependence of lightabsorptivity (photoelectric conversion rate) in silicon.

FIG. 5 is a graph illustrating comparison in light-receiving angledistribution characteristic between a first-type separating regionformed by impurity ion implantation and a second-type separating regionformed with an oxide film.

FIG. 6 is a plotted graph illustrating the added value of output signalsof a first portion and a second portion of each photoelectric conversionelement to which the first-type separating region is applied, withincident light varying in wavelength.

FIG. 7 is a plotted graph illustrating the added value of output signalsof a first portion and a second portion of each photoelectric conversionelement to which the second-type separating region is applied, withincident light varying in wavelength.

FIG. 8 is an illustration for describing the variation of an opticalpath due to the film width of the second-type separating region.

FIG. 9 is a graph illustrating a simulated result of the relationshipbetween the film width of the second-type separating region and relativesensitivity.

FIG. 10 is an illustration for describing an exemplary method ofmanufacturing the solid-state image pickup element.

FIG. 11 is an illustration for describing an exemplary method ofmanufacturing the solid-state image pickup element.

FIG. 12 is an illustration for describing an exemplary method ofmanufacturing the solid-state image pickup element.

FIG. 13 is an illustration for describing an exemplary method ofmanufacturing the solid-state image pickup element.

FIG. 14 is a block diagram of the configuration of one embodiment of anelectronic apparatus to which the present technology is applied.

FIG. 15 is an illustration of exemplary combinations of a pixel to whichthe first-type separating region is applied and a pixel to which thesecond-type separating region is applied.

FIG. 16 is an illustration of exemplary combinations of a pixel to whichthe first-type separating region is applied and a pixel to which thesecond-type separating region is applied.

MODE FOR CARRYING OUT THE INVENTION

The present technology will be described below in accordance with thefollowing order.

(A) First Embodiment:

(B) Second Embodiment:

(C) Third Embodiment:

(A) First Embodiment

FIG. 1 is a plan view of the pixel arrangement of a solid-state imagepickup element according to the present embodiment, and FIG. 2 is aschematic view of the sectional configuration of the solid-state imagepickup element according to the present embodiment. Note that, althoughthe present embodiment will be described with an exemplaryback-illuminated solid-state image pickup element, the presenttechnology can be also achieved as a front-illuminated solid-state imagepickup element including a photoelectric conversion element PD to bedescribed below.

The solid-state image pickup element 100 includes a plurality of pixelseach including a photodiode as an embedded photoelectric conversionelement PD formed on a silicon semiconductor substrate 10.

The semiconductor substrate 10 is provided with an element separator 12along the boundary between the respective unit pixel regions of theplurality of pixels. The element separator 12 has a structure in which asilicon dioxide film is embedded in a trench formed by engraving thesemiconductor substrate 10 or a structure in which a silicon dioxidefilm and metal are embedded in a trench formed by engraving thesemiconductor substrate 10. This arrangement can inhibit color mixturebetween pixels more than an element separator formed by impurity ionimplantation does.

Moreover, for some pixels in the plurality of pixels, the photoelectricconversion element PD formed in one of the unit pixel regions (regionsrespectively surrounded by the element separators 12) is furtherseparated by a partition structure including a first-type separatingregion SP1 or a second-type separating region SP2.

Such pixels PX1 each have the photoelectric conversion element PDpartitioned into a first portion PD1 and a second portion PD2 by thefirst-type separating region SP1 extending in a plate shape in adirection Dd along the thickness direction of the semiconductorsubstrate 10. Other pixels PX2 each have the photoelectric conversionelement PD partitioned into the first portion PD1 and the second portionPD2 by the second-type separating region SP2 extending in a plate shapein the direction Dd along the thickness direction of the semiconductorsubstrate 10.

The number of separated portions of the photoelectric conversion elementPD in one unit pixel region separated by the first-type separatingregion SP1 or the second-type separating region SP2 is required to betwo or more. For example, there are an aspect in which a separating filmis formed in the photoelectric conversion element PD in one unit pixelregion to divide the photoelectric conversion element PD into two, andan aspect in which two separating films intersecting in a cross shape inplan view are formed in the photoelectric conversion element PD in oneunit pixel region to divide the photoelectric conversion element PD intofour. Dividing a photoelectric conversion element PD formed in one unitpixel region into two results in a so-called 2 photo diode (2PD)structure.

The first-type separating region SP1 and the second-type separatingregion SP2 each include a silicon dioxide film or an impurity ionimplanted region. The present embodiment will be described below mainlywith an exemplary case where the first-type separating region SP1includes an impurity ion implanted region and the second-type separatingregion SP2 includes a silicon dioxide film.

In addition, in the example illustrated in FIG. 2, a wiring layer 20 islayered on the surface 10F side of the semiconductor substrate 10, andan insulating layer 30, a color filter layer 40 including a plurality ofcolor filters 41 to 43, and an on-chip lens layer 50 including aplurality of on-chip lenses 51 to 53, are layered in this order on theback face 10R side of the semiconductor substrate 10.

The wiring layer 20 is a so-called multilayer wiring layer including aplurality of wiring layers disposed through an interlayer insulatingfilm. Because no light is incident on the wiring layer side, a wiringlayout can be designed flexibly.

The insulating layer 30 is formed with, for example, an antireflectioncoating. The antireflection coating is formed with a plurality of filmshaving different refractive indices, and is formed with, for example,two films of a hafnium dioxide (HfO₂) film and a silicon dioxide film. Alight-shielding film 31 is provided at the position along the boundaryportion between the unit pixel regions and in the shape thereof, on theinsulating layer 30. The light-shielding film 31 required to include alight-shielding material is preferably formed with a film of metal, suchas aluminum (Al), tungsten (W), or copper (Cu), as a material having astrong light-shielding effect and capable of being precisely processedby micromachining, for example, etching.

A planarization film is formed on the insulating layer 30 including thelight-shielding film 31. Then, in succession on the planarization film,the color filter layer 40 is formed and the on-chip lens layer 50 isformed on the color filter layer 40. For example, the on-chip lenses 51to 53 are formed with an organic material, such as resin. For example,the planarization film can be formed with an organic material, such asresin. For example, the on-chip lenses 51 to 53 each have alight-condensing characteristic in which the beam waist of condensedlight thereof is formed in the thickness range of the semiconductorsubstrate 10.

The color filters 41 to 43 included in the color filter layer 41selectively transmit any color selected from a plurality of mutuallydifferent colors (e.g., red, green, and blue), and are, for example,color filters in the Bayer arrangement. The color of a color filter willbe described below as the color of a pixel with a pixel having a redcolor filter as a red pixel, a pixel having a green color filter as agreen pixel, and a pixel having a blue color filter as a blue pixel.Incident light on the solid-state image pickup element 100 is incidenton the on-chip lens layer 50 side, and the respective beams of lightthat have been condensed by the on-chip lenses 51 to 53 and have beentransmitted through the color filters 41 to 43 are received by thephotoelectric conversion elements PD.

The color filters 41 to 43 and the on-chip lenses 51 to 53 are providedat respective positions corresponding to the unit pixel regions. Anotherlayer may be provided between the semiconductor substrate 10 and thewiring layer 20, and another layer may be provided each between thesemiconductor substrate 10, the insulating layer 30, the color filterlayer 40, and the on-chip lens layer 50.

FIG. 3 illustrates results of an optical-path simulation of incidentlight for photoelectric conversion elements PD separated with differentseparating films. FIG. 3(a) illustrates the separating films each formedwith an impurity ion implanted region, and FIG. 3(b) illustrates theseparating films each formed with a silicon dioxide film. The respectivenumerical values indicated on the vertical axis and the horizontal axisare in units of 10 nm.

The optical path for first-type separating regions SP1 formed byimpurity ion implantation (FIG. 3(a)) is substantially similar to thatin a case where no first-type separating region SP1 is provided. This isbecause there is no variation in refractive index between silicon thatis the material of the semiconductor substrate 10 and a silicon dioxidefilm that is the material of each first-type separating region SP1. Inother words, for each pixel separated by the first-type separatingregion SP1, the incident light incident on the back face 10R of thesemiconductor substrate 10 after condensation by the on-chip lens isincident on a substantially center of the photoelectric conversionelement PD of the pixel. Then, the incident light travels in a directionsubstantially perpendicular to a substrate face and reflects on thesurface 10F of the semiconductor substrate 10, to travel in the oppositedirection through substantially the same optical path.

Meanwhile, for each second-type separating region SP2 formed by theoxide film (FIG. 3(b)), with the optical path branching to both sides ofthe second-type separating region SP2, the light travels whilerepeatedly reflecting between the boundary of the element separator 12and the boundary the second-type separating region SP2 as reflectivefaces. This is because there is a difference in refractive index betweenambient silicon that is the material of the semiconductor substrate 10and the second-type separating region SP2.

Here, because each second-type separating region SP2 is formed only tothe middle of a depth of the semiconductor substrate 10 (a range ofapproximately 2 to 2.5 μm in the numerical value on the vertical axis inFIG. 3), there is a gap between the second-type separating region SP2and the surface 10F of the semiconductor substrate 10 (a range ofapproximately 2.5 to 4 μm in the numerical value on the vertical axis ofFIG. 3).

Thus, when the light travels exceeding the formed depth of thesecond-type separating region SP2, there is a possibility that the lightthat has traveled in the first portion PD1 of the photoelectricconversion element PD partitioned by the second-type separating regionSP2, travels reflectively to the adjacent second portion PD2.Conversely, there is a possibility that the light that has traveled inthe second portion PD2 of the photoelectric conversion element PDpartitioned by the second-type separating region SP2, travelsreflectively to the adjacent first portion PD1. In other words, there isa possibility that optical color mixture occurs on both sides of thesecond-type separating region SP2.

FIG. 4 is a graph illustrating the wavelength dependence of lightabsorptivity (photoelectric conversion rate) in silicon. As illustratedin the figure, silicon has a tendency that the light absorptivityincreases with light shorter in wavelength and the light absorptivitydecreases with light longer in wavelength. As a result, light is morelikely to travel to the surface 10F side with respect to the formeddepth of the second-type separating region SP2 in order of decreasingwavelength (red>green>blue), and optical color mixture is more likely tooccur on both sides of the second-type separating region SP2 with lightshorter in wavelength.

As a result, it can be understood that adjustment of the length in thedepth direction of the second-type separating region SP2 enablesadjustment of the degree of inhibition of color mixture ofshort-wavelength light. For example, a length of 0.5 μm or more in thedepth direction of second-type separating region SP2, more preferably, alength of 1 μm thereof can inhibit light that is 400 nm or less inwavelength, from causing optical color mixture on both sides of thesecond-type separating region SP2.

Furthermore, because the element separator 12 is formed only to themiddle of the depth of the semiconductor substrate 10 (a range ofapproximately 2 to 2.5 μm in the numerical value on the vertical axis ofFIG. 3), a gap is formed between the second-type separating region SP2and the surface 10F of the semiconductor substrate 10 (a range ofapproximately 2.5 to 4 μm in the numerical value on the vertical axis ofFIG. 3).

Thus, when light travels exceeding the formed depth of the elementseparator 12, there is a possibility that the light that has traveled inone pixel partitioned by the element separator 12, travels reflectivelyto another pixel. In other words, there is a possibility that colormixture occurs between the adjacent pixels partitioned by the elementseparator 12.

Furthermore, light is more likely to travel to the surface 10F side withrespect to the formed depth of the element separator 12 in order ofdecreasing wavelength (red>green>blue), and color mixture is more likelyto occur between the adjacent pixels partitioned by the elementseparator 12 with light shorter in wavelength.

As a result, it can be understood that adjustment of the length in thedepth direction of the element separator 12 enables adjustment of thedegree of inhibition of color mixture of short-wavelength light. Forexample, a length of 0.5 μm or more in the depth direction ofsecond-type separating region SP2, more preferably, a length of 1 μmthereof can inhibit light that is 400 nm or less in wavelength, fromcausing optical color mixture on both sides of the second-typeseparating region SP2. Further desirably, the element separator 12 isformed such that the length thereof reaches the surface 10F of thesemiconductor substrate 10.

Although the element separator 12 having a length reaching the surface10F of the semiconductor substrate 10 can be formed from the back face10R side of the semiconductor substrate 10 as described above, theelement separator 12 can be formed with a structure in which a silicondioxide film is embedded in a trench formed from the surface 10F side ofthe semiconductor substrate 10 or with a structure in which a silicondioxide film and metal are embedded in a trench formed from the surface10F side of the semiconductor substrate 10.

With adoption of a technique of forming the element separator 12 fromthe surface 10F side, formation of the second-type separating region SP2from the back face 10R side causes no concern that a previously formedtrench groove causes irregularity of swept resist. Furthermore, thesecond-type separating region SP2 having a degree of length not reachingthe surface 10F, formed from the back face 10R side enables escape ofsaturated and overflowing electrons from one side to the other sidebetween the first portion PD1 and the second portion PD2 of thephotoelectric conversion element PD partitioned by the second-typeseparating region SP2.

FIG. 5 is a graph illustrating comparison in light-receiving angledistribution characteristic between the first-type separating region SP1formed by impurity ion implantation (implantation separation L andimplantation separation R) and the second-type separating region SP2formed with an oxide film (oxide-film separation L and oxide-filmseparation R).

From the figure, it can be understood that the second-type separatingregion SP2 is lower than the first-type separating region SP1 in termsof occurrence of color mixture at general light-receiving angles. Thisis because, in the case of using the first-type separating region SP1,whereas light propagates on the first-type separating region SP1similarly to the silicon, electrons generated by photoelectricconversion on the first-type separating region SP1 at a potential higherthan that of the silicon, moves to either the first portion PD1 or thesecond portion PD2 due to a probabilistic behavior, resulting indeterioration of the isolation of light-receiving angle distribution.

FIG. 6 is a plotted graph illustrating the added value of output signalsof the first portion PD1 and the second portion PD2 of eachphotoelectric conversion element PD to which the first-type separatingregion SP1 is applied, with incident light varying in wavelength. FIG. 7is a plotted graph illustrating the added value of output signals of thefirst portion PD1 and the second portion PD2 of each photoelectricconversion element PD to which the second-type separating region SP2 isapplied, with incident light varying in wavelength. The relativespectral level indicated along the vertical axis in FIGS. 6 and 7indicates, with a peak value in the output signal of a G pixel as thenormalization factor (100%), the output signals of the other pixels topercentage.

As illustrated in FIG. 6, each photoelectric conversion element PD towhich the first-type separating region SP1 is applied, indicates alight-receiving characteristic substantially equivalent to that of eachphotoelectric conversion element PD provided with no separating film.

As illustrated in FIG. 7, for the photoelectric conversion elements PDto which the second-type separating region SP2 is applied, optical colormixture occurs between the red pixel and the Gr pixel (green pixeladjacent to the red pixel) and optical color mixture occurs between theblue pixel and the Gb pixel (green pixel adjacent to the blue pixel), incomparison to photoelectric conversion elements PD provided with noseparating film. However, it is observed that each photoelectricconversion element PD has a light-receiving characteristic substantiallyequivalent to that of each photoelectric conversion element PD providedwith no separating film, at less than a wavelength of 480 nm, and eachphotoelectric conversion element PD has a light-receiving characteristicdifferent from that of each photoelectric conversion element PD providedwith no separating film, at a wavelength of 480 nm or more. Furthermore,a shift occurs between the Gr pixel and the Gb pixel at a wavelength of600 nm or more.

FIG. 8 is an illustration for describing the variation of an opticalpath due to the film width of the second-type separating region SP2.FIG. 8(a) illustrates an optical-path simulation in a case where thefilm width of the second-type separating region SP2 is 120 nm, and FIG.8(b) illustrates an optical-path simulation in a case where the filmwidth of the second-type separating region SP2 is 320 nm.

From the figures, it can be understood that light propagating inside thesecond-type separating region SP2 is longer in penetration depth and theamount of light propagating inside the second-type separating region SP2is larger in the case where the film width of the second-type separatingregion SP2 is 320 nm, than in the case where the film width of thesecond-type separating region SP2 is 120 nm. In other words, it can beunderstood that, as the film width of the second-type separating regionSP2 increases, the amount of light incident on the first portion PD1 andthe second portion PD2 of the photoelectric conversion element PDdecreases.

FIG. 9 is a graph illustrating a simulated result of the relationshipbetween the film width of the second-type separating region SP2 andrelative sensitivity. The relative sensitivity indicated in the figureis normalized by the sensitivity in a case where light at 400 nm isperpendicularly (0 degree) incident on a photoelectric conversionelement PD to which the first-type separating region SP1 is applied. Asillustrated in the figure, the relative sensitivity is substantially 1at a film width of approximately 400 nm or less of second-typeseparating region SP2, and the relative sensitivity is approximately 0.8or more at a film width of approximately 550 nm or less of second-typeseparating region SP2.

In other words, it can be understood that the second-type separatingregion SP2 having a film width equal to or less than the wavelength ofvisible light inhibits light propagation inside the second-typeseparating region SP2 as quickly as possible. Furthermore, it can beunderstood that the second-type separating region SP2 having a filmwidth equal to or less than the wavelength of blue light may achieve arelative sensitivity of 0.9 or more. Furthermore, it can be understoodthat the second-type separating region SP2 having a film width equal toor less than the wavelength of green light may achieve a relativesensitivity of 0.8 or more.

In consideration of the characteristics, it can be understood that thepixel PX1 to which the first-type separating region SP1 is applied andthe pixel PX2 to which the second-type separating region SP2 is applied,can be selected with various combinations in accordance with uses.Exemplary specific combinations will be described below with referenceto FIGS. 15 and 16, but variations on combinations are not limited tothese.

Examples of a first specific combination are, as illustrated in FIG.15(a), the photoelectric conversion elements PD of a red pixel and greenpixels to which the first-type separating region SP1 is applied and thephotoelectric conversion element PD of a blue pixel to which thesecond-type separating region SP2 is applied.

Thus, application of the second-type separating region SP2 to aphotoelectric conversion element PD serving photoelectric conversion ofblue light short in wavelength, enables achievement of favorableisolation of light-receiving angle distribution for blue light, andapplication of the first-type separating region SP1 to a photoelectricconversion element PD serving photoelectric conversion of green light orred light close to longer wavelength, can inhibit color mixture due toincidence of light reflected after arrival at the vicinity of thesurface 10F, on an adjacent area partitioned by a separating film or anelement separating region. At this time, the film width of thesecond-type separating region SP2 to be applied to the blue pixel isdesirably the wavelength of blue light (approximately 400 nm) or less.

An example of a second specific combination is, as illustrated in FIG.15(b), a case where the first-type separating region SP1 is applied tothe photoelectric conversion element PD of a red pixel and thesecond-type separating region SP2 is applied to each of thephotoelectric conversion elements PD of green pixels and a blue pixel.

Thus, application of the second-type separating region SP2 to the greenpixels in addition to the blue pixel, enables favorable isolation oflight-receiving angle distribution for the green pixels, and enablesacquisition of an advantage that auto focus precision with on-sensorphase-difference improves in a case where a subject has the contrast ofa green-wavelength region.

Examples of a third specific combination are, as illustrated in FIG.16(c), the photoelectric conversion elements PD of a Gb pixel and a bluepixel to which the second-type separating region SP2 is applied and thephotoelectric conversion elements PD of a Gr pixel and a red pixel towhich the first-type separating region SP1 is applied.

Thus, application of the second-type separating region SP2 to the bluepixel and the Gb pixel and application of the first-type separatingregion SP1 to the red pixel and the Gr pixel, enables, only for the bluepixel, color mixture due to incidence of light reflected after arrivalat the vicinity of the surface 10F, on an adjacent area partitioned by aseparating film or an element separating region, so that the combinationis suitable for a case where red in color is regarded as important fromthe viewpoint of image forming and the like. At this time, alignment ofthe partitions of the second-type separating regions SP2 in a directionorthogonal to the direction in which the Gb pixel and the blue pixel aredisposed in parallel, results in an advantage that the Gr pixel and theGb pixel having different types of separating films, have no adverseeffect on calculation for a shift amount in on-sensor phase-difference.

Examples of a fourth specific combination are, as illustrated in FIG.16(d), the photoelectric conversion elements PD of a red pixel and a Gbpixel to which the first-type separating region SP1 is applied, and thephotoelectric conversion elements PD of a blue pixel and a Gr pixel towhich the second-type separating region SP2 is applied.

Thus, application of the second-type separating region SP2 to the bluepixel and the Gr pixel and application of the first-type separatingregion SP1 to the red pixel and the Gb pixel, enables, only for the redpixel, color mixture due to incidence of light reflected after arrivalat the vicinity of the surface 10F, on an adjacent area partitioned by aseparating film or an element separating region, so that the combinationis suitable for a case where blue in color is regarded as important fromthe viewpoint of image forming and the like. Furthermore, thepartitioning directions of the second-type separating regions SP2,orthogonal to the direction in which the Gr pixel and the red pixel aredisposed in parallel, results in an advantage that the Gr pixel and theGb pixel having different types of separating films, have no adverseeffect on calculation for a shift amount in on-sensor phase-difference.

The configuration of, for example, a pixel transistor for outputtingcharge accumulated in each photoelectric conversion element PD in thesolid-state image pickup element described above, can adopt a circuitconfiguration described in Japanese Patent Application Laid-Open No.2015-65269, for example.

(B) Second Embodiment

Next, an exemplary method of manufacturing the solid-state image pickupelement according to the first embodiment will be described withreference to FIGS. 10 to 13.

First, photodiodes as photoelectric conversion elements PD are formed byion implantation in a two-dimensional arrangement having atwo-dimensional matrix, from the surface 10F side of a semiconductorsubstrate 10. For example, a p-type semiconductor well region is formedin contact with an element separating region in which an elementseparator is to be formed, in a region corresponding to eachphotoelectric conversion element PD on the surface 10F of thesemiconductor substrate 10, and a plurality of pixel transistors isformed in each p-type semiconductor well region. The pixel transistorseach are formed with a source region, a drain region, a gate insulatingfilm, and a gate electrode. Note that illustrations of the photoelectricconversion elements PD and the pixel transistors are omitted in FIGS. 10to 13.

Next, a resist mask R is formed on the surface 10F of the semiconductorsubstrate 10, and impurity ion implantation is performed from above theresist mask R. The resist mask R has openings R1 in areas in which theelement separator 12, first-type separating regions SP1, and second-typeseparating regions SP2 are to be formed. Impurity ion regions Dp1, eachhaving a width corresponding to the opening R1, are formed in apredetermined depth range of the semiconductor substrate 10 by theimpurity ion implantation.

Next, a wiring layer 20, including a plurality of wiring layers disposedthrough an interlayer insulating film, is layered on the surface 10F ofthe semiconductor substrate 10. An interlayer insulating film, such as aSiO₂ film, is layered on the wiring layer 20, and the interlayerinsulating film is planarized by chemical mechanical polishing (CMP), sothat the surface of the wiring layer 20 is formed to a substantiallyplanarized face.

Next, a support substrate SB is stuck onto the substantially planarizedface of the wiring layer 20, so that reinforcement is made. Asemiconductor substrate, such as bulk silicon, is used for the supportsubstrate SB, for example. Note that, in a case where part of aperipheral circuit or the entirety thereof is formed on a peripheralcircuit substrate separately manufactured, the peripheral circuitsubstrate is stuck on the surface of the wiring layer 20, and thesupport substrate SB is stuck on the peripheral circuit substrate. Then,the semiconductor substrate 10, on which the support substrate SB isstuck, is turned upside down, so that the back face 10R of thesemiconductor substrate 10 is set to an upper face.

Next, removal processing is performed by grinding and polishing from theback face 10R of the semiconductor substrate 10 to the vicinity of theback faces of the photoelectric conversion elements PD. Finally, theback face 10R of the semiconductor substrate 10 is processed by CMP soas to be substantially planarized. Note that the final-stage processingcan be performed by etching.

Next, a silicon dioxide film HM is formed as a hard mask on the backface 10R of the semiconductor substrate 10, and openings HM1 are formed,by lithography and etching, at only portions at which the second-typeseparating regions SP2 are to be formed. The silicon dioxide film as thehard mask can be formed, for example, by high density plasma (HDP),plasma tetra ethyl oxysilane (P-TEOS), or the like.

Next, the back face 10R of the semiconductor substrate 10 is subjectedto anisotropic dry etching through the hard mask, resulting in formationof trenches T included in the ranges of the impurity ion regions Dp1 atthe portions at which the second-type separating regions SP2 are to beformed. In other words, the entire wall face of each trench T is coveredwith the impurity ion region Dp1 in shape. After the formation of thetrenches T, the hard mask is removed, for example, by wet etching.

Next, a negatively fixed charged membrane is deposited on the back face10R of the semiconductor substrate 10 and the entire wall face of eachtrench T. As the negatively fixed charged membrane, use of a materialcapable of generating fixed charge to reinforce pinning, due toaccumulation onto a substrate such as silicon, is preferable, and ahigh-refractive-index material film or a high dielectric film havingnegative charge can be used. As a specific material, for example, anoxide or a nitride including at least one element of hafnium (Hf),aluminum (Al), zirconium (Zr), tantalum (Ta), or titanium (Ti), can beapplied. Examples of deposition methods include a chemical vapordeposition method (hereinafter, referred to as a CVD), a sputteringmethod, an atomic layer deposition method (hereinafter, referred to asan ALD), and the like. Use of the ALD method enables simultaneousformation of a film thickness of approximately 1 nm of SiO₂ film thatreduces an interface state during deposition. Furthermore, examples ofmaterials other than the materials include an oxide and a nitride eachincluding at least one element of lanthanum (La), praseodymium (Pr),cerium (Ce), neodymium (Nd), promethium (Pm), samarium (Sm), europium(Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho),thulium (Tm), ytterbium (Yb), lutetium (Lu), or yttrium (Y). Moreover,the fixed charged membrane can be formed with a hafnium oxynitride filmor an aluminum oxynitride film. For each material for the fixed chargedmembrane described above, silicon (Si) or nitrogen (N) may be added intothe film within the range in which the insulating property is notdamaged. The concentration thereof is appropriately determined in therange in which the insulating property of the film is not damaged. Thus,addition of silicon (Si) or nitrogen (N) enables improvement of thethermal resistance and the capability of blocking ion implantation in aprocess, of the film.

Next, an oxide film is embedded into the trenches T, and an oxide filmF1 layered on the back face 10R of the semiconductor substrate 10 isremoved by etchback. At this time, the oxide film F1 deposited on theback face 10R of the semiconductor substrate 10, partially remains,resulting in a thin oxide film F2 covering the back face 10R. Thus, withthe thin oxide film F2 remaining between a light-shielding film CM1 tobe described later and the silicon of the semiconductor substrate 10,increase of the distance between the light-shielding film CM1 and thesilicon of the semiconductor substrate 10, allows improvement in adarkness characteristic.

Next, a barrier metal film and a metal film are deposited as thelight-shielding-film material layer CM1 on the oxide film F2 of thesemiconductor substrate 10. The barrier metal film is formed with Ti,TiN, Ta, or TaN, for example, by a sputtering method or a CVD method.For example, the metal is formed with Cu, W, or Al by an electrolyticplating method. Then, a resist mask is formed selectively on thelight-shielding-film material layer CM1. The resist mask is processed toremain on regions to be protected from light, such as a region fordetermination of black level, a peripheral-circuit region, and a regionalong the boundary of a pixel. The light-shielding-film material layernot covered with the resist mask is removed by lithography and etching,to form a light-shielding film CM2.

Next, a planarization film PF is formed on the light-shielding film CM2so as to cancel difference in level, and color filters 41 to 43 areformed in succession on the planarization film. The planarization filmPF is intended to avoid irregularity that occurs in the spin-coatingsequence of the color filters 41 to 43, but the difference in level isnot necessarily cancelled as long as the irregularity is allowable. Theplanarization film PF can be deposited, for example, by spin coating ofa resin material, but an inorganic film, such as SiO₂, may be depositedand planarization may be performed by CMP. It is considered that, forexample, pigment or dye is spin-coated for the color filters 41 to 43and may be arranged in the Bayer arrangement or the like. However, thearrangement of the color filters 41 to 43 is not limited thereto.

Next, on-chip lenses 51 to 53 are formed on the color filters 41 to 43.Examples of the material of the on-chip lenses 51 to 53 include astyrene-based resin, an acrylic resin, a styrene-acrylic copolymerresin, a siloxane-based resin, and the like that are organic material,but the material of the on-chip lenses 51 to 53 is not limited to these.For lens-shape formation, a photoresist, for example, a photosensitivematerial with a novolak resin as a main component, is patterned bylithography. The pattern-formed resist is subjected to heat treatment ata temperature higher than the thermal softening point, to form lensshape. With the lens-shaped resist as a mask, the lens shape ispattern-transferred to a primary lens material with a dry etchingmethod, and lenses are formed to all pixels. However, the formation isnot limited to this technique. For example, a method of performingdeposition of a lens material including a photosensitive resin, prebake,exposure, development, and bleaching exposure processing in succession,and then performing heat treatment at a temperature not less than thethermal softening point of the photosensitive resin, may be used.

The solid-state image pickup element according to the first embodimentdescribed above can be fabricated with the manufacturing methoddescribed above.

(C) Third Embodiment

FIG. 14 is a block diagram of the configuration of one embodiment of anelectronic apparatus to which the present technology is applied.

As illustrated in FIG. 14, an image pickup device 300 as the electronicapparatus includes: an optical unit 311 including, for example, a lensgroup; a solid-state image pickup element 312; and a digital signalprocessor (DSP) 313 that is a camera signal processing circuit.Furthermore, the image pickup device 300 includes a frame memory 314, adisplay unit 315, a recording unit 316, an operation unit 317, a powerunit 318, and a control unit 319. The DSP 313, the frame memory 314, thedisplay unit 315, the recording unit 316, the operation unit 317, thepower unit 318, and the control unit 319 are mutually connected througha communication bus.

The optical unit 311 receives incident light (image light) from asubject, to form an image on the image pickup face of the solid-stateimage pickup element 312. The solid-state image pickup element 312converts the amount of light of the incident light with which the imageis formed on the image pickup face by the optical unit 311, into anelectric signal in units of pixels, and outputs a color-component signalfor forming an image signal indicating the image of the subject, as apixel signal. Furthermore, the solid-state image pickup element 312outputs a phase-difference detection signal to be used forphase-difference auto focus (AF), as a pixel signal. As the solid-stateimage pickup element 312, a solid-state image pickup element, such asthe solid-state image pickup element 100 according to the firstembodiment described above, can be used.

The display unit 315 including a panel-type display device, such as aliquid crystal panel or an organic electro luminescence (EL) panel, forexample, displays a still image or a moving image captured by thesolid-state image pickup element 312. The recording unit 316 records thestill image or the moving image captured by the solid-state image pickupelement 312, into a recording medium, such as a flash memory.

The operation unit 317 issues an operation command for various functionsincluded in the image pickup device 300, in accordance with an operationof a user. The power unit 318 appropriately supplies various powersources to be operation power sources for the DSP 313, the frame memory314, the display unit 315, the recording unit 316, the operation unit317, and the control unit 319, to the objects to be supplied with.

The control unit 319 controls the operation of each unit of the imagepickup device 300. Furthermore, the control unit 319 performspredetermined computing with the phase-difference detection signal fromthe solid-state image pickup element 312, to calculate the amount ofdefocus, and controls the driving of, for example, a shooting lensincluded in the optical unit 311, for an in-focus state in accordancewith the amount of defocus. This arrangement allows performance of thephase-difference AF, resulting in focusing on the subject.

Note that, each embodiment described above has been given exemplarilywith the present technology applied to a CMOS image sensor includingunit pixels disposed in a matrix, each being to detect signal chargecorresponding to the amount of light of visible light, as a physicalquantity. However, the present technology is not limited to applicationto the CMOS image sensor, and thus can be applied to general solid-stateimage pickup elements with photoelectric conversion elements PD.

Furthermore, the present technology is not limited to application to asolid-state image pickup element that detects the distribution of theamount of incident light of visible light to capture an image. Thepresent technology can be applied to a solid-state image pickup elementthat captures the amount of incidence of, for example, infrared rays,X-rays, or particles, as an image, and, as the general meaning, generalsolid-state image pickup elements, such as a fingerprint detectionsensor that detects the distribution of a different physical quantity,such as pressure or electrostatic capacitance, to capture an image(physical-quantity distribution detection devices).

Note that the present technology is not limited to each embodimentdescribed above, and includes, for example, a configuration in whicheach configuration disclosed in each embodiment described above ismutually replaced with another configuration or an alternation is madein combination and a configuration in which a publicly known technologyand each configuration disclosed in each embodiment described above aremutually replaced or an alternation is made in combination. Furthermore,the technical scope of the present technology is not limited to theembodiments described above, but covers the matters described in thescope of the claims and equivalents thereof.

Then, the present technology can have the following configurations.

(1)

A solid-state image pickup element including:

a plurality of pixels each including a photoelectric conversion elementformed on a silicon substrate,

in which some pixels in the plurality of pixels each have thephotoelectric conversion element partitioned by a first-type separatingregion extending in a plate shape in a direction along a thicknessdirection of the silicon substrate, and

other pixels in the plurality of pixels each have the photoelectricconversion element partitioned by a second-type separating region formedwith a material different from a material of the first-type separatingregion, the second-type separating region extending in a plate shape inthe direction along the thickness direction of the silicon substrate.

(2)

The solid-state image pickup element described in (1) above, in whichthe pixels each having the photoelectric conversion element partitionedby the first-type separating region are different in color from thepixels each having the photoelectric conversion element partitioned bythe second-type separating region.

(3)

The solid-state image pickup element described in (1) or (2) above, inwhich the plurality of pixels includes a combination of a red pixel, ablue pixel, and a green pixel,

the pixels each having the photoelectric conversion element partitionedby the second-type separating region, include the blue pixel, and

the pixels each having the photoelectric conversion element partitionedby the first-type separating region, include the red pixel and the greenpixel.

(4)

The solid-state image pickup element described in (1) or (2) above, inwhich the second-type separating region having the plate shape includesa silicon dioxide film, the second-type separating region having a platethickness equal to or less than a wavelength of blue light.

(5)

A method of manufacturing a solid-state image pickup element thatincludes a plurality of pixels each including a photoelectric conversionelement formed on a silicon substrate, the method including:

a step of forming a first-type separating region extending in a plateshape in a direction along a thickness direction of the siliconsubstrate, the first-type separating region partitioning thephotoelectric conversion element of each of some pixels in the pluralityof pixels; and

a step of forming a second-type separating region with a materialdifferent from a material of the first-type separating region, thesecond-type separating region extending in a plate shape in thedirection along the thickness direction of the silicon substrate, thesecond-type separating region partitioning the photoelectric conversionelement of each of other pixels in the plurality of pixels.

(6)

An electronic apparatus including:

a solid-state image pickup element that includes a plurality of pixelseach including a photoelectric conversion element formed on a siliconsubstrate,

in which some pixels in the plurality of pixels each have thephotoelectric conversion element partitioned by a first-type separatingregion extending in a plate shape in a direction along a thicknessdirection of the silicon substrate, and

other pixels in the plurality of pixels each have the photoelectricconversion element partitioned by a second-type separating region formedwith a material different from a material of the first-type separatingregion, the second-type separating region extending in a plate shape inthe direction along the thickness direction of the silicon substrate.

REFERENCE SIGNS LIST

-   10 Semiconductor substrate-   10F Surface-   10R Back face-   12 Element separator-   20 Wiring layer-   30 Insulating layer-   31 Light-shielding film-   40 Color filter layer-   41 to 43 Color filter layers-   50 On-chip lens layer-   51 to 53 On-chip lenses-   100 Solid-state image pickup element-   300 Image pickup device-   311 Optical unit-   312 Solid-state image pickup element-   313 Digital signal processor (DSP)-   314 Frame memory-   315 Display unit-   316 Recording unit-   317 Operation unit-   318 Power unit-   319 Control unit-   CM1 Light-shielding-film material layer-   CM2 Light-shielding film-   Dp1 Impurity ion region-   F1 Oxide film-   F2 Oxide film-   HM Silicon dioxide film-   HM1 Opening-   PD Photoelectric conversion element-   PF Planarization film-   PD1 First portion-   PD2 Second portion-   PX1 Pixel-   PX2 Pixel-   R Resist mask-   R1 Opening-   SB Support substrate-   SP1 First-type separating region-   SP2 Second-type separating region-   T Trench

The invention claimed is:
 1. A light detecting device, comprising:first, second, third, and fourth pixels disposed adjacent to each otherin a plan view, wherein the first pixel includes a first photoelectricconversion region partitioned by a first separation region, wherein thesecond pixel includes a second photoelectric conversion regionpartitioned by a second separation region, wherein the third pixelincludes a third photoelectric conversion region partitioned by a thirdseparation region, wherein the fourth pixel includes a fourthphotoelectric conversion region partitioned by a fourth separationregion, wherein a material of the first separation region is differentfrom a material of the second separation region, wherein a material ofthe third separation region is a same material as a material of thesecond separation region, and wherein the first separation regionincludes an impurity ion implanted region.
 2. The light detecting deviceaccording to claim 1, wherein the second separation region includes asilicon oxide film, and wherein the third separation region includes asilicon oxide film.
 3. The light detecting device according to claim 1,wherein, in the plan view, the fourth separation region has a crossshape.
 4. The light detecting device according to claim 1, wherein thefirst pixel is a red pixel.
 5. A light detecting device, comprising:first, second, third, and fourth pixels disposed adjacent to each otherin a plan view, wherein the first pixel includes a first photoelectricconversion region partitioned by a first separation region, wherein thesecond pixel includes a second photoelectric conversion regionpartitioned by a second separation region, wherein the third pixelincludes a third photoelectric conversion region partitioned by a thirdseparation region, wherein the fourth pixel includes a fourthphotoelectric conversion region partitioned by a fourth separationregion, wherein a material of the first separation region is differentfrom a material of the second separation region, and wherein the firstpixel is a red pixel.
 6. The light detecting device according to claim5, wherein a material of the third separation region is a same materialas a material of the second separation region.
 7. The light detectingdevice according to claim 5, wherein the first separation regionincludes an impurity ion implanted region.
 8. The light detecting deviceaccording to claim 5, wherein the second separation region includes asilicon oxide film.
 9. The light detecting device according to claim 5,wherein a material of the second, third, and fourth separation regionsare the same.
 10. The light detecting device according to claim 5,wherein the second and third pixels are green pixels.
 11. The lightdetecting device according to claim 10, wherein the fourth pixel is ablue pixel.
 12. The light detecting device according to claim 5, whereinthe second separation region includes a silicon oxide film, and whereinthe third separation region includes a silicon oxide film.
 13. The lightdetecting device according to claim 5, wherein, in the plan view, thefourth separation region has a cross shape.
 14. The light detectingdevice according to claim 13, wherein the second and third pixels aregreen pixels.
 15. A light detecting device, comprising: first, second,third, and fourth pixels disposed adjacent to each other in a plan view,wherein the first pixel includes a first photoelectric conversion regionpartitioned by a first separation region, wherein the second pixelincludes a second photoelectric conversion region partitioned by asecond separation region, wherein the third pixel includes a thirdphotoelectric conversion region partitioned by a third separationregion, wherein the fourth pixel includes a fourth photoelectricconversion region partitioned by a fourth separation region, wherein amaterial of the first separation region is different from a material ofthe second separation region, and wherein, in the plan view, the fourthseparation region has a cross shape.
 16. The light detecting deviceaccording to claim 15, wherein a material of the third separation regionis a same material as a material of the second separation region. 17.The light detecting device according to claim 15, wherein the firstseparation region includes an impurity ion implanted region.
 18. Thelight detecting device according to claim 15, wherein the secondseparation region includes a silicon oxide film.
 19. The light detectingdevice according to claim 15, wherein the second separation regionincludes a silicon oxide film, and wherein the third separation regionincludes a silicon oxide film.
 20. The light detecting device accordingto claim 15, wherein a material of the second, third, and fourthseparation regions are the same.